Exemplary embodiments of the present invention relate to a solid propellant gas generator, an extinguishing device, a method for cooling a flowing mixture and a method for extinguishing a fire.
Solid propellant gas generators are known in systems for extinguishing fires. In this case an extinguishing medium, which is present in the form of a solid propellant in a capsule, is ignited, so that the ignition process causes a flowing mixture of, for example, aerosols and gases, which are suitable for extinguishing or suppressing a fire, to develop from the solid propellant. In addition, the ignited solid propellant acts as a propellant for expelling the mixture from the capsule, in order to help extinguish or suppress the fire by means of the resulting increased kinetic energy of the mixture. An exemplary solid propellant gas generator for use in extinguishing fires is described in German patent document DE 31 22 897 A1.
The process of igniting the solid propellant, however, causes a significant rise in the temperature of the aerosols or rather the gases, so that the flowing mixture is released into the surrounding area at a high temperature. Such a situation should be avoided, especially if persons or temperature sensitive machines may be found in the outlet area of the flowing mixture.
Therefore, the solid propellant gas generators that are currently available on the market use cooling systems that cool the flowing mixture down to acceptable temperatures. Frequently solid thermal storage mediums, such as metal or ceramic, that can absorb the heat of the flowing mixture, are used for such cooling purposes. In that case the amount of thermal energy that can be stored is usually directly proportional to the weight of the storage medium.
However, the net effect is an increase in the weight of the solid propellant gas generators, so that they are less suitable for use in the design and construction of aircrafts.
Therefore, exemplary embodiments of the present invention are directed to an improved solid propellant gas generator.
A solid propellant gas generator is designed for releasing a flowing mixture from a solid propellant, separated from a surrounding area, into the surrounding area and comprises a cooling system for cooling the flowing mixture. In this case the cooling system has at least one feed device for feeding and mixing a gas from the surrounding area with the flowing mixture prior to entering into the surrounding area.
When the flowing mixture is released from the solid propellant gas generator, the flowing mixture absorbs energy and, in so doing, heats up too much. By supplying a gas, which has a lower energy content, from the surrounding area, the flowing mixture can be cooled to lower temperatures. In the case of the solid propellant gas generator according to the invention, the cooled gas from the surrounding area is mixed with the flowing mixture before the flowing mixture enters into the surrounding area. This arrangement reduces the risk of persons getting burned and/or the risk of temperature sensitive machines being damaged in the outlet region into the surrounding area. Accordingly, heavy cooling systems made of metal or ceramic for cooling purposes are not required. As a result, the solid propellant gas generator can also be used in the field of aeronautics.
Preferably the cooling system comprises an acceleration device for accelerating the flowing mixture, an introducing device for introducing the flowing mixture into the surrounding area and preferably a linear contact region of acceleration device and introducing device. In one advantageous embodiment the feed device is arranged at the contact region.
Thus, the kinetic energy, which the flowing mixture absorbs upon acceleration in the acceleration device, can be utilized through a reduction in the pressure for the purpose of drawing in cooling gas from the surrounding area by means of the feed device.
Preferably the feed device is arranged radially to the contact region. In particular, it is provided that the cross-section of the feed device tapers off from the surrounding area in the direction of the contact region.
Hence, the cooling gas from the surrounding area can be fed preferably essentially perpendicular to the flow direction of the flowing mixture, as a result of which the cooling gas mixes with the flowing mixture.
Due to the advantageous design of the feed device in the tapering form, the gas from the surrounding area is additionally accelerated in the direction of the flowing mixture, as a result of which an even better mixing of the mixture and gas is achieved.
Preferably the acceleration device connects an interior of the solid propellant gas generator with the contact region. At the same time it is provided that the cross-section of the acceleration device tapers off from the interior in the direction of the contact region.
Due to the advantageous design of the acceleration device the flowing mixture from the interior is accelerated in the direction of the contact region, where the mixture mixes with the cooling gas from the surrounding area.
Furthermore, the introducing device connects the contact region with the surrounding area. In this case the cross-section of the introducing device expands from the contact region in the direction of the surrounding area.
Due to the advantageous expansion of the introducing device, the previously accelerated flowing mixture is introduced into the surrounding area with dissimilar directional components and can mix there with the cooling gas from the surrounding area. The net effect is a drop in the temperature of the flowing mixture.
In a preferred embodiment the cooling system comprises a sealing mechanism for sealing off the interior from the surrounding area. In particular, the sealing mechanism is a water impermeable foil. This arrangement prevents contaminants from the surrounding area from penetrating into the cooling system or more specifically the solid propellant gas generator and, for example, clogging the cooling system.
It is most highly preferred that the feed device is arranged at the cooling system in the flow direction of the flowing mixture downstream of the sealing mechanism. Thus, on igniting the solid propellant the sealing mechanism can be blasted free by means of the flowing mixture that is generated. Therefore, it is even more preferred that the sealing mechanism be disposed in the region of the acceleration device, in particular at the place, where the flowing mixture reaches a maximum speed.
The cross-section of the cooling system is designed so as to taper off in the flow direction of the flowing mixture. Due to the advantageous outer shape of the cooling system, cool ambient air is conveyed along the tapering outer walls of the cooling system to the region, in which the flowing mixture enters into the surrounding area. Hence, it is possible to generate turbulence that enables the cool ambient air to mix with the flowing mixture.
Preferably a solid propellant storage device is provided for storing the solid propellant; and the housing of this solid propellant storage device is provided with a thermal insulation. With this solid propellant storage device the solid propellant can be separated from the surrounding area; and at the same time a thermal insulation is also on hand. During the ignition process this thermal insulation can ensure that the activating energy, generated by the ignition process, is used to generate the flowing mixture and is not released into the surrounding area. This minimizes both a rise in the temperature of the generator jacket and the risk of injuring persons and damaging material.
To this end an igniting device for igniting the solid propellant for generating the flowing mixture is provided.
In a preferred embodiment the solid propellant gas generator has a solid propellant for generating a gas and/or an aerosol and/or a gas-aerosol mixture, in particular for producing an extinguishing agent.
It is most highly preferred that a filter unit, in particular a metal mesh, is arranged between the cooling system and the solid propellant. With this arrangement it is possible to prevent the solid particles, which are produced when the solid propellant is ignited or when the solid propellant does not completely burn off, from clogging the cooling system, in that the solid particles are retained on the filter unit in the interior of the solid propellant gas generator.
An extinguishing device for extinguishing a fire comprises the solid propellant gas generator described above.
In a method for cooling a flowing mixture the following steps are carried out:    a) accelerating the flowing mixture;    b) feeding a cooling gas into the flowing mixture; and    c) distributing the cooled flowing mixture into a surrounding area in such a way that additional cooling gas is supplied.
The acceleration of the flowing mixture, the supply of cooling gas and the distribution of the cooled flowing mixture is made possible by providing the solid propellant gas generator described above.
In this respect it is highly preferred that the flowing mixture be filtered.
In an advantageous method for extinguishing a fire preferably the steps a) to c) of the above described method are carried out.